The present invention relates to the anchoring of ligament replacements or soft tissue in bone tunnels, and more particularly to a cross pin and a method of fixing the cross pin which facilitates securing a replacement graft inside a bone and that promotes healing of the graft inside the bone.
When a ligament such as an anterior cruciate ligament (hereinafter "ACL") of a knee is damaged or torn, a replacement ligament is often installed in the knee to reconstruct the natural ACL. During such reconstruction, with the knee bent appropriately, a tunnel is typically drilled through the anterior portion of the tibia upwardly through the tibial plateau and into the distal end of the femur to approximate the natural position of the ACL, in accordance with well known surgical techniques. A bone-ligament-bone graft is then harvested, often from the patellar tendon following standard grafting techniques, all well known in the orthopaedic field. Typically, a wedge-shaped bone-ligament-bone graft is cut and contoured using a graft guide.
Various fixation methods are known in the orthopaedic field for securing a bone-ligament-bone graft within the tibia and femur so that the graft can heal. For example, it is known to use a pin installed transversely to the bone tunnel to secure the replacement ligament within the tunnel such as that shown in U.S. Pat. No. 5,397,356 entitled "Pin for Securing a Replacement Ligament to a Bone" to E. Marlowe Goble and Jerry L. Lower. Also, methods for installing such a cross pin are shown in U.S. Pat. No. 5,139,520 entitled "Method for ACL Reconstruction" to Thomas D. Rosenberg; U.S. Pat. No. 5,562,671 entitled "Ligament Replacement Cross Pinning Method" to E. Marlowe Goble and Jerry L. Lower; and U.S. Pat. No. 5,350,380 entitled "Method for Securing a Ligament Replacement in a Bone" to E. Marlowe Goble and Jerry L. Lower. The devices and methods disclosed in these patents are incorporated herein by reference. These types of pins often operate by holding and forcing the bone block at the end of the replacement ligament against the wall of the tunnel, essentially wedging the bone block in place. In other known methods, sutures coupled to the graft are anchored to the bone using screws or washers. The replacement ligaments can also be coupled directly to the bone using plates or washers in conjunction with a bone screw. Alternatively, the replacement ligament can be secured by interference screw fixation, as disclosed in U.S. Pat. No. 4,950,270 entitled "Cannulated Self-Tapping Bone Screw" to Jerald A. Bowman and Richard V. Zile.
Other materials which can be used as replacement ligaments include the gracilis tendon, semitendinosus tendon, and small intestine submucosa (hereinafter "SIS). U.S. Pat. No. 4,902,508 entitled "Tissue Graft Composition" to Stephen F. Badylak, et al.; U.S. Pat. No. 5,281,422 entitled "Graft for Promoting Autogenous Tissue Growth" to Stephen F. Badylak, et al.; and U.S. Pat. No. 5,611,969 entitled "Large Area Submucosal Tissue Graft Constructs" to Umesh H. Patel, et al. describe harvesting and preparation of SIS grafts. The methods and materials disclosed in these patents are incorporated herein by reference. While these graft materials perform well, prior art procedures for inserting and securing such material are time consuming. Also, in situations where previous reconstruction has been performed, a new femoral tunnel placed close to the previous tunnel may not allow for fixation methods such as interference screw fixation.
Replacement ligaments can be secured within the femoral tunnel without the use of a bone plug by looping the replacement ligament over a cross pin.
A tendon threader, such as those described in U.S. Pat. Nos. 5,266,075 entitled "Tendon Threader for Endosteal Ligament Mounting" to Ron Clark and Raymond E. Olsen; and U.S. Pat. No. 5,601,562 entitled "Forked Insertion Tool and Method of Arthroscopic Surgery Using the Same" to Eugene M. Wolf and Richard D. Grafton, can be used to form a loop in the replacement ligament and to position the replacement ligament within the femoral tunnel so that the loop may be captured by the cross pin. The devices and methods disclosed in these patents are incorporated herein by reference.
Methods which use a cross pin to secure a looped replacement ligament are effective, especially in situations in which there had been a previous reconstruction. Unfortunately, existing cross pins were not designed for this purpose. Generally, they were designed to wedge a bone block into the medial wall of the bone tunnel. These pins were not designed to be inserted easily into a graft loop, and they were not designed to hold the graft material in contact with the femoral wall, which would insure better ingrowth.
The graft fixation method and cross pin of the present invention provide advantages over the prior fixation methods and pins. The pin includes two tapered portions, a body, and a threaded portion. In the illustrated embodiment, the first tapered portion is long, relatively narrow, has a gentle taper, and can be inserted easily through the transversely drilled hole and into the graft insertion tool, where it captures the loop of the replacement ligament more easily than prior pins. The first tapered portion also inserts easily into the medial side of the femur. Because the first tapered portion is relatively narrow, it may eliminate the need for a guidewire during insertion of the pin.
In the illustrated embodiment, the second tapered portion is substantially shorter and has a more severe taper than the first tapered portion. Also, as illustrated, the body portion is cylindrical, but body portions with other shapes may be acceptable. As the cross pin is inserted, the wider second tapered portion compresses the replacement ligament against the wall of the femoral tunnel. The body of the cross pin then holds the replacement ligament against the wall. Thus, the present invention insures better ingrowth and provides a more secure fixation technique than previously found. An additional advantage of the current invention is that the second tapered portion provides resistance when it meets the medial wall of the femoral tunnel, thus signaling when the cross pin is fully seated. Another advantage of the current fixation method and pin is that rigid fixation afforded by the cross pin allows the patient immediately to bear weight and start range of motion exercises.
Also in the illustrated embodiment, when the cross pin is fully seated, the threaded portion will be buried in the femur, and the proximal end of the cross pin will be flush with the lateral surface of the femur. However, a cross pin having a head which may protrude from the lateral surface of the femur is also within the scope of this invention. Such a head may aid in installation or may be useful for later removal of the pin.
The present invention also includes a method for installing the cross pin. By using the illustrated method, a surgeon may insert the looped replacement ligament into the femoral tunnel, capture the loop with the cross pin with relative ease, and seat the cross pin at the appropriate depth. The method results in a replacement ligament which is held securely in the femoral tunnel, in such a way as to insure rapid ingrowth.
Additional objects, features, and advantages of the present invention will become apparent from the following description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.